A metallic wire is commonly coated by passing the wire through a bath of molten metal, such as molten zinc, molten zinc alloy, or molten aluminum. After emerging from the molten metal bath, the wire is drawn through a gas wiping nozzle, in order to obtain a uniform metal coating upon the substrate metal, by wiping the excess of molten metal.
Such a gas wiping nozzle is e.g. disclosed in EP-A-0 357 297. The nozzle has an upper annular part and a lower annular part. Each of the annular parts have an upper and lower surface meeting in a substantially sharp annular edge, adjacent surfaces of the upper and lower annular parts defining between them an annular gas passage operatively connected to a source of pressurized gas and terminating in an annular gas orifice. The edges and the gas orifice define a wire orifice through which passes a wire coated with molten metal, which is therein wiped by the gas blown through the gas passage.
This gas wiping nozzle is efficient for wiping excess molten metal from the surface of a wire, but it can be easily damaged by molten metal. Indeed, during the coating process, the molten metal coated wire is generally drawn along a drawing axis centered in the wire orifice. The molten metal coated wire can deviate from its drawing axis and contacts directly the annular gas passage, the molten metal thence filling in the gas passage, solidifying therein and therefore obstructing it. From that point on, the molten metal coated wire passing through the nozzle is not properly wiped and does no longer meet the quality requirements. The gas wiping nozzle has to be cleaned or replaced.